Multiple endocrine neoplasia-type 1 (MEN1) is an autosomal dominant familial cancer syndrome characterized by tumors in parathyroids, enteropancreatic endocrine tissues, and the anterior pituitary. DNA sequencing from a previously identified minimal interval on chromosome 11q13 identified several candidate genes, one of which contained 12 different frameshift, nonsense, missense, and in-frame deletion mutations in 14 probands from 15 families. The MEN1 gene contains 10 exons and encodes a ubiquitously expressed 2.8-kilobase transcript. The predicted 610-amino acid protein product, termed menin, exhibits no apparent similarities to any previously known proteins. The identification of MEN1 will enable improved understanding of the mechanism of endocrine tumorigenesis and should facilitate early diagnosis.

MEN1 is a tumor suppressor gene that encodes a 610 amino acid nuclear protein (menin) of previously unknown function. Using a yeast two-hybrid screen with menin as the bait, we have identified the transcription factor JunD as a direct menin-interacting partner. Menin did not interact directly with other Jun and Fos family members. The menin-JunD interaction was confirmed in vitro and in vivo. Menin repressed transcriptional activation mediated by JunD fused to the Gal4 DNA-binding domain from a Gal4 responsive reporter, or by JunD from an AP1-responsive reporter. Several naturally occurring and clustered MEN1 missense mutations disrupted menin interaction with JunD. These observations suggest that menin's tumor suppressor function involves direct binding to JunD and inhibition of JunD activated transcription.

Primary hyperparathyroidism is a common disorder with an annual incidence of approximately 0.5 in 1,000 (ref. 1). In more than 95% of cases, the disease is caused by sporadic parathyroid adenoma or sporadic hyperplasia. Some cases are caused by inherited syndromes, such as multiple endocrine neoplasia type 1 (MEN1; ref. 2). In most cases, the molecular basis of parathyroid neoplasia is unknown. Parathyroid adenomas are usually monoclonal, suggesting that one important step in tumour development is a mutation in a progenitor cell. Approximately 30% of sporadic parathyroid tumours show loss of heterozygosity (LOH) for polymorphic markers on 11q13, the site of the MEN1 tumour suppressor gene. This raises the question of whether such sporadic parathyroid tumours are caused by sequential inactivation of both alleles of the MEN1 gene. We recently cloned the MEN1 gene and identified MEN1 germline mutations in fourteen of fifteen kindreds with familial MEN1 (ref. 10). We have studied parathyroid tumours not associated with MEN1 to determine whether somatic mutations in the MEN1 gene are present. Among 33 tumours we found somatic MEN1 gene mutation in 7, while the corresponding MEN1 germline sequence was normal in each patient. All tumours with MEN1 gene mutation showed LOH on 11q13, making the tumour cells hemi- or homozygous for the mutant allele. Thus, somatic MEN1 gene mutation for the mutant allele. Thus, somatic MEN1 gene mutation contributes to tumorigenesis in a substantial number of parathyroid tumours not associated with the MEN1 syndrome.

Multiple endocrine neoplasia type 1 is an autosomal dominant tumor syndrome. Manifestations include neoplasms of the parathyroid glands, enteropancreatic neuroendocrine cells, and the anterior pituitary gland. The MEN1 tumor suppressor gene encodes menin, a 610 amino acid nuclear protein without sequence homology to other proteins. To elucidate menin function, we used immunoprecipitation to identify interacting proteins. The NF-kB proteins p50, p52 and p65 were found to interact speci®cally and directly with menin in vitro and in vivo. The region of NF-kB proteins sucient for binding to menin is the N-terminus. Furthermore, amino acids 305 ± 381 of menin are essential for this binding. Menin represses p65-mediated transcriptional activation on NFkB sites in a dose-dependent and speci®c manner. Also, PMA (phorbol 12-myristate 13-acetate)-stimulated NFkB activation is suppressed by menin. These observations suggest that menin's ability to interact with NF-kB proteins and its modulation of NF-kB transactivation contribute to menin's tumor suppressor function. Oncogene (2001) 20, 4917 ± 4925.

Lung carcinoids occur sporadically and rarely in association with multiple endocrine neoplasia type 1 (MEN1). There are no well defined genetic abnormalities known to occur in these tumors. We studied 11 sporadic lung carcinoids for loss of heterozygosity (LOH) at the locus of the MEN1 gene on chromosome 11q13, and for mutations of the MEN1 gene using dideoxy fingerprinting. Additionally, a lung carcinoid from a MEN1 patient was studied. In four of 11 (36%) sporadic tumors, both copies of the MEN1 gene were inactivated. All four tumors showed the presence of a MEN1 gene mutation and loss of the other allele. Observed mutations included a 1 bp insertion, a 1 bp deletion, a 13 bp deletion and a single nucleotide substitution affecting a donor splice site. Each mutation predicts truncation or potentially complete loss of menin. The remaining seven tumors showed neither the presence of a MEN1 gene mutation nor 11q13 LOH. The tumor from the MEN1 patient showed LOH at chromosome 11q13 and a complex germline MEN1 gene mutation. The data implicate the MEN1 gene in the pathogenesis of sporadic lung carcinoids, representing the first defined genetic alteration in these tumors.

Although there is indirect genetic evidence that MEN1, the gene for multiple endocrine neoplasia type 1, is a tumor suppressor gene, little is known about the MEN1-encoded protein, menin. Menin was stably overexpressed in a well-characterized murine tumor cell line, (valine-12)-RAS-transformed NIH3T3 cells. Menin overexpression reverted the morphology of the RAS-transformed NIH3T3 cells towards the more¯attened and more spread, ®broblastic shape of wild type NIH3T3 cells. The proliferation rate of the RAS-transformed cells in 0.5% calf serum was also slower with menin overexpression. Menin overexpression reduced the RASinduced clonogenicity in soft agar. Menin also reduced tumor growth after injection of cells in nude mice. In conclusion, stable overexpression of MEN1 suppressed partially the RAS-mediated tumor phenotype in vitro and in vivo. Overexpressed menin protein had biological eects, directly supporting MEN1 gene function as a tumor suppressor.

Objectives: We retrospectively reviewed 5 patients with neurosarcoidosis, who all presented with central diabetes insipidus and hypogonadism. Design: This was a single-centre, retrospective analysis of 5 cases with a minimum follow-up of 2 years. Methods: Case analysis included clinical, biochemical, and endocrinological evaluation and frequent CT/MRI scans of involved organs as primary evaluation and in response to immunosuppressive therapy. Result: Neurosarcoidosis was diagnosed in all patients. Two patients had no proven extracerebral manifestation and had a stable disease over 3 and 5 years. One patient showed deterioration with corticosteroids alone but partial remission after additional cyclophosphamide. Pituitary dysfunction remained unchanged in all patients, despite total clinical and radiological remission in two patients. However, one of these patients died of acute granulomatous meningoencephalitis after two years of follow-up. Conclusion: Although the presenting symptoms of neurosarcoidosis may vary, the occurrence of central diabetes insipidus associated with typical radiological features is suggestive of neurosarcoidosis. However, there is an increasing number of case reports on lymphocytic hypophysitis. Without the bioptic diagnosis, the differentiation between potentially lethal isolated neurosarcoidosis and lymphocytic hypophysitis is difficult. These cases demonstrate the difficulties in diagnosing neurosarcoidosis and reflect experiences with follow-up parameters.

Adrenocortical tumors occur as sporadic tumors, as part of the multiple endocrine neoplasia type 1 (MEN1) syndrome or as part of other hereditary disorders. We recently cloned the MEN1 gene, a tumor-suppressor gene located on chromosome 11q13. Subsequently, we showed that sequential somatic inactivation of both alleles of the MEN1 gene contributes to the development of some sporadic endocrine neoplasms (parathyroid, enteropancreatic neuroendocrine, bronchial carcinoid, and pituitary tumors). We now studied whether somatic inactivation of the MEN1 gene contributes to the pathogenesis of sporadic adrenocortical neoplasms. Seven adrenocortical carcinomas, 2 adrenocortical carcinoma cell lines, and 11 aldosterone-secreting, 8 cortisol-secreting, and 5 nonsecreting benign adrenocortical tumors were studied. Seven tumors (5 of 5 carcinomas, 2 of 21 nonsecreting benign adenomas; P < 0.001) exhibited loss of heterozygosity on 11q13. All 33 tumors and cell lines were screened for mutation throughout the MEN1 open-reading frame and adjacent splice junctions. None exhibited a mutation within the MEN1-coding region. We conclude that somatic MEN1 mutation within the MEN1-coding region does not occur commonly in sporadic adrenocortical tumors, although the majority of adrenocortical carcinomas exhibit 11q13 loss of heterozygosity.